<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>buju_text</title>
    <style>
        *{
            /* 内边距和外边距 */
            padding: 0;
            margin: 0;
        }
        body{
            display: flex;
            /* 排列方向 */
            flex-direction: column;
            /* 对齐方式 */
            justify-content: space-between;
            height: 100vh;
        }

        header{
            height: 100px;
            background-color: cyan;
        }
        main{
            /* flex-grow 属性用于设置或检索弹性盒子的扩展比率 */
            flex-grow: 1;
            background-color: darkcyan;

        }
        footer{
            height: 70px;
            background-color: darkorange;
        }



    </style>
</head>
<body>
    <header></header>
    <main>
        <a>这是主体</a>
    </main>
    <footer></footer>
</body>
</html>